diff --git a/problems/0028.实现strStr.md b/problems/0028.实现strStr.md index 69f8c9d6..fc14a34a 100644 --- a/problems/0028.实现strStr.md +++ b/problems/0028.实现strStr.md @@ -808,7 +808,93 @@ func strStr(haystack string, needle string) int { } ``` +JavaScript版本 +> 前缀表统一减一 + +```javascript +/** + * @param {string} haystack + * @param {string} needle + * @return {number} + */ +var strStr = function (haystack, needle) { + if (needle.length === 0) + return 0; + + const getNext = (needle) => { + let next = []; + let j = -1; + next.push(j); + + for (let i = 1; i < needle.length; ++i) { + while (j >= 0 && needle[i] !== needle[j + 1]) + j = next[j]; + if (needle[i] === needle[j + 1]) + j++; + next.push(j); + } + + return next; + } + + let next = getNext(needle); + let j = -1; + for (let i = 0; i < haystack.length; ++i) { + while (j >= 0 && haystack[i] !== needle[j + 1]) + j = next[j]; + if (haystack[i] === needle[j + 1]) + j++; + if (j === needle.length - 1) + return (i - needle.length + 1); + } + + return -1; +}; +``` + +> 前缀表统一不减一 + +```javascript +/** + * @param {string} haystack + * @param {string} needle + * @return {number} + */ +var strStr = function (haystack, needle) { + if (needle.length === 0) + return 0; + + const getNext = (needle) => { + let next = []; + let j = 0; + next.push(j); + + for (let i = 1; i < needle.length; ++i) { + while (j > 0 && needle[i] !== needle[j]) + j = next[j - 1]; + if (needle[i] === needle[j]) + j++; + next.push(j); + } + + return next; + } + + let next = getNext(needle); + let j = 0; + for (let i = 0; i < haystack.length; ++i) { + while (j > 0 && haystack[i] !== needle[j]) + j = next[j - 1]; + if (haystack[i] === needle[j]) + j++; + if (j === needle.length) + return (i - needle.length + 1); + } + + return -1; +}; +``` diff --git a/problems/0459.重复的子字符串.md b/problems/0459.重复的子字符串.md index f012811d..25b52e86 100644 --- a/problems/0459.重复的子字符串.md +++ b/problems/0459.重复的子字符串.md @@ -289,8 +289,79 @@ func repeatedSubstringPattern(s string) bool { } ``` +JavaScript版本 +> 前缀表统一减一 +```javascript +/** + * @param {string} s + * @return {boolean} + */ +var repeatedSubstringPattern = function (s) { + if (s.length === 0) + return false; + + const getNext = (s) => { + let next = []; + let j = -1; + + next.push(j); + + for (let i = 1; i < s.length; ++i) { + while (j >= 0 && s[i] !== s[j + 1]) + j = next[j]; + if (s[i] === s[j + 1]) + j++; + next.push(j); + } + + return next; + } + + let next = getNext(s); + + if (next[next.length - 1] !== -1 && s.length % (s.length - (next[next.length - 1] + 1)) === 0) + return true; + return false; +}; +``` + +> 前缀表统一不减一 + +```javascript +/** + * @param {string} s + * @return {boolean} + */ +var repeatedSubstringPattern = function (s) { + if (s.length === 0) + return false; + + const getNext = (s) => { + let next = []; + let j = 0; + + next.push(j); + + for (let i = 1; i < s.length; ++i) { + while (j > 0 && s[i] !== s[j]) + j = next[j - 1]; + if (s[i] === s[j]) + j++; + next.push(j); + } + + return next; + } + + let next = getNext(s); + + if (next[next.length - 1] !== 0 && s.length % (s.length - next[next.length - 1]) === 0) + return true; + return false; +}; +``` diff --git a/problems/剑指Offer58-II.左旋转字符串.md b/problems/剑指Offer58-II.左旋转字符串.md index 8a60252c..fe4c3473 100644 --- a/problems/剑指Offer58-II.左旋转字符串.md +++ b/problems/剑指Offer58-II.左旋转字符串.md @@ -165,41 +165,26 @@ func reverse(b []byte, left, right int){ ``` -javaScript: +JavaScript: -```js -/** - * @param {string} s - * @param {number} n - * @return {string} - */ - var reverseLeftWords = function(s, n) { - const strArr = Array.from(s); - reverse(strArr, 0, n - 1); - reverse(strArr, n, strArr.length - 1); - reverse(strArr, 0, strArr.length - 1); - return strArr.join(''); +```javascript +var reverseLeftWords = function (s, n) { + const reverse = (str, left, right) => { + let strArr = str.split(""); + for (; left < right; left++, right--) { + [strArr[left], strArr[right]] = [strArr[right], strArr[left]]; + } + return strArr.join(""); + } + s = reverse(s, 0, n - 1); + s = reverse(s, n, s.length - 1); + return reverse(s, 0, s.length - 1); }; - -// 翻转从 start 到 end 的字符 -function reverse(strArr, start, end) { - let left = start; - let right = end; - - while(left < right) { - // 交换 - [strArr[left], strArr[right]] = [strArr[right], strArr[left]]; - left++; - right--; - } -} ``` - - ----------------------- * 作者微信:[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw) * B站视频:[代码随想录](https://space.bilibili.com/525438321)